Data centres typically generate high levels of internal heat. It is therefore necessary to provide cooling means in order to keep the IT equipment that they house functioning within the prescribed environmental limits.
Adiabatic cooling is used in known data centre cooling systems because it can substantially increase the power efficiency of the data centre relative to the use of other cooling means, for example DX cooling, thereby substantially reducing operating costs.
Air is cooled adiabatically by humidification: water is exposed to warm air and energy is transferred from the warm air to the water resulting in the water transforming from a liquid to a gaseous state. This process results in humidified air of lower temperature than the original warm air, with no heat energy having been added or removed from the system.
In order for adiabatic cooling to be most effective, the rate of evaporation of water should be maximised; this is achieved by maximising the surface area of water exposed to the air flow that requires cooling. Known adiabatic cooling systems maximise this surface area by spraying a water mist into the air or by passing the air through a wettable matrix.
A problem related to the use of wettable matrix evaporative humidifiers is retention of water within the wettable matrix after the water supply has been cut-off; there is a time lag between the command for dry air being given and dry air being delivered to the data centre. This time lag directly affects the accuracy with which the data centre temperature and humidity levels can be controlled and can result in over cooling of the data centre.
When an evaporative humidifier is used in conjunction with DX cooling, the problem of over humidification could be reduced by enabling a ‘dehumidification mode’; this, however, would be very power intensive.
A cooling method proposed in WO2011/148175 suggests the use of automated dampers to bypass the evaporative humidifier which might mitigate the effects of the time lag, but it is believed that there is scope for yet further improvement on how the humidity levels can be controlled.
The present invention seeks to mitigate one or more of the above-mentioned problems. Alternatively or additionally, the present invention seeks to provide a method for providing cooling air of closely controlled humidity to a data centre and apparatus therefor.